The little bit of lathe work can be done with emery cloth using the shoeshine method.

I'll see about a set up to get the barrel out.

OK -- just above the barrel on the inside of the upper are two dimples for the return springs. Cut two rods that will jam between these and the rear of the lower. This will support the sheet metal upper when the upper and lower are together and lets you put pressure on the barrel.

From the inside, the barrel's rearmost ring flushes with the inside of the upper.

There is no nonsense so errant that it cannot be made the creed of the vast majority by adequate governmental action. -- Bertrand Russell

"Never attribute to malice that which can be adequately explained by stupidity."Robert J. Hanlon

"If they’re going to come here illegally, apply for & receive assistance through a corrupted Government agency encouraging this lawless behavior, work under the table & send billions of dollars each year back to their families in Mexico, while bleeding local economies dry, protest in our streets waving their Mexican flags DEMANDING rights, while I have to press ’1′ for English, then they need to be shipped back to where they came from!" -Chad Miller